Arc-controlling thermostat



Oct. 21, 1930.

M. L. PATTERSON ARC CONTROLLING THERMOSTAT Filed Nov. 5, 1921 gmvemtoz MART/NZ Hqrrmsm Patented Oct. 21, 1930 UNITED 'STATES PATENT, OFFICE MARTIN L. PATTERSON, 0F BOGOTA, NEW JERSEY, ASSIGNOR, BY MESNE ASSIGN- MEN'IS, TO SPERRY GYROSCOPE COMPANY, INC., A CORPORATION OF NEW YORK ARC-CONTROLLING THERMOSTA'I Application filed November 5, 1921. Serial No. 513,149.

This invention relates to thermostats for use in controlling the feeding or positioning of the electrodes in arc lamps. Thermostats are used in searchlights and other are lights where the light source or the tip of one of the electrodes is maintained substantially in a S fixed position. The thermostat is so placed with respect to the light source that the light when in the focal position will shine upon it to open or close a circuit connected with-the electrode feeding mechanism, or it may be that the thermostat is normally shielded from the light but is engaged thereby when the light source recedes from the focal point; the action of the thermostat then serving to open or close the circuit to effect the feeding of one of the electrodes.

Thermostats of this natureusuallycomprise a pair of thermostatic strips, one of which is exposed to the light when the latter is in a given position as we have seen, while the other is shielded from said light. Expansion or contraction of the strips due to changes in temperature of the surrounding medium is equal in the two strips and the result is neutral, but a greater expansion or contraction of one of the strips causes relative movement of the contacts. Such thermostats are known as compensating thermostats.

The object of the present invention is to improve upon the structure of such thermostats, to.render them less susceptible to vibrations, and at the same time to simplify and cheapen their construction, without impairing their sensitiveness as thermostats.

Referring to the drawings wherein I have shown what I now consider ferred form of my invention:

Fig. 1 is a sectional side elevation of a thermostat constructed in accordance with my invention.

Fig. 2 is a rear elevation thereof.

Fig. 3 is a sectional view taken on line 3-3 of Fig.1. I

Fig. 4 is a diagrammatic view of the thermostat, the are light and the wiring.

Figs. 5 and 6 are diagrammatic representations of the thermostat in differentpositions.

t b th 0 e 6 pre plate 15 itself.

Fig. 7 is a detail view of the thermostatic elements. In the drawings, lrepresentsthethermostat casing. Within this casing is shown an insulating block 2 to which is secured an arm 3. aid arm may be composed of a pair of thermostatic elements 4, 5 and an amplifying arm 6. The thermostatic elements are in turn of the bi-metallic type, such as shown in Fig. 7, wherein two pieces of metal 7, 8, having different coefficients of expansion are integrally joined together by means of solder or other suitable method. These elements may in turn be secured together end-to-end by slightly overlapping their ends and clamping them together as shown by plates 9, 10 and rivets 11. The outer end of element 5 may be bent as shown and the arm 6 may be attached to the bent over portion, so as to project downward- 131 into the depending part 13 of casing 1. Preferably the arm 6 is provided with a stiffening rib or fold 6 so that the amplifying arm will not become easily bent or warped.

Said arm is also preferably formed of a single metal so as not to possess any properties of the thermostatic strips, said arm acting only to amplify the movements of the outer end of the thermostatic stri 5. Thelower end of arm 6 is provided wlth an electrical contact 14. In securing the thermostatic'member to block 2 the rear portion of element 4 may be placed upon the block and a more rigid plate 15 placed on the top thereof and clamped down by screw 16. The rear portion 17 of plate 15 is bent downwardly against the back of the block, the width of the depending portion 17 being somewhat less than that of the Opposite contact 14 is a-cooperating contact 18 which may be carried on an arm 19. The said arm may be clamped between the upper and lower portions of block 2 and separated from the screw 20 which secures the block to the casing 1 byymeans of an insulating bushing 21 passing through a hole in the arm.

'A strip 22 of arm 19 may be bent over the back of block 2, reaching upwardly adjacent the bent-over portion17 of plate .15. An adjusting screw 23 enga 'ng the back of arm 19 but insulated there rom by insulation 24 may be provided to adjust the position of contact 18 with respect to contact 14. The arm 19, of course, presses resiliently against the adjusting screw so as to follow when the screw is retracted.

It will be noted that the casing 1 is divided into two portions 1 and 1 secured together by screws 25, and that the thermostatic elements are carried by the portion 1*.

The portion 1 is shown as provided with binding posts 26,- 27 insulated therefrom in the usual manner as at 28. Secured to the posts within the casing are resilient contact rushes 29, 30 adapted to register with the bent-over portions 22 and 17 when the portions of the casing are assembled.

Insulation lining 43, 44 may be provided on the inside of the casing walls opposite the loose ends of arms 6 and 19 to prevent grounding of the contacts should these arms be caused to move against said walls.

Holes 31 may be provided in the casing so that the contacts 14, 18 may be observed when desired and to permit circulation of air through the casing. Adjacent one of the thermostatic elements, as for instance element 5, a window 32 is shown in the casing to permit a beam of light to shineonly upon said element.

The relative positions of the thermostat and the are light are shown in Fig. 4. In this figure a lens 33 is shown as located between the light source 34 and the thermostat. When the end of the positive electrode 35 is inthe desired position at 34, the light passing through lens 33 will be focused upon the casing at a point 36 near window 32 as indicated by dotted lines 36', but when the electrode burns back to the position represented by line 37 for instance, the concentrated light beam will move upon the element 5 as indicated by dot and dash lines 37 The action of the thermostat is illustrated diagrammatically in Figs. 5 and 6. It is of course understood, that the bi-me'tallic elements 4, 5 will curve when they become heated, by reason of the diiference in the degree of expansion of the two metals; the convex side being thatwhich is comprised of the metal having the greater expansion. Thus, by placing the elements 4, 5 in reverse positions so that in element 4 the metal havin the greater degree of expansion will face ownwardly and that of element 5 upwardly, the behavior of the device due to heat of the air surroundtacts 14, 18 are,.,normally open they willremain so, and it will be seen that fluctuations -in temperature of the surrounding medium will have no affect "upon the thermostat.

When the beam from the light is cast upon "the element 5, however, greater'curvature of that element will immediately take place as in Fig. 6 and arm 6 will be actuated to move contact 14 into engagement with contact 18.

Fig. 4 includes a simple form of wiring which may be used for the thermostat. Here the contact 14 is shown connected by wire 38 to one of the feed lines 39, while contact 18 is connected by wire 40 through an electromagnet or solenoid 41 to the other line 42. Closure of contacts 14, 18 will thus affect energization of the electromagnet which may in turn control the electrode feeding mechanism.

A condenser 45 may be shunted across the contacts 14, 18 by being connected to the binding posts 26, 27, to prevent sparking when the contacts open.

While I have shown the arm 19 as reaching from contact 18 to block 2, it is obvious that this particular construction is a mere matter of convenience in carrying current from the binding post 27 to contact 18. The arm at the same time serves as a spring and cooperates with the screw 23 in adjusting the contact. v

As shown in Fig. 3, the thermostatic elements 4, 5, instead of being narrow, may be comparatively wide. This will lend rigidity to the structure and render it less susceptible to vibrations which might otherwise cause untimely closure of contacts 14,18- Also, the thermostatic elements may be slit as shown at 46 to prevent the elements from becoming distorted.

In accordance with the provisions of the Patent Statutes, I have herein described the principle of my invention, together with the apparatus, which I now consider to represent the best embodiment thereof, but I desire to have it understood that the apparatus shown is only illustrative and that the invention can be carried out byother means. Also, while it is designed to use the various features and elements in the combination and relations described, some of these may be altered and others omitted without interfering with the more general results outlined, and the invention extends to such use.

Having described my invention, what I claim and desire to secure by Letters Patent 1S9 1. A thermostat for controlling the feeding of arc electrodes, comprising a base member, an arm comprising reversely disposed thermostatic strips rigidly joined together end-to-end and reversely positioned, one end of: said arm being fixedly secured to said member, a contact carried by the opposite end of said arm,a second strip carried by said base member and a cooperating contact carried by said second strip.

2. In an arc controlling thermostat, a casing, a pair of oppositely disposed thermostatic elements rigidly secured end-to-end to each otherto form a strip, one end of said strip being fixedly secured to said casing, the other end thereof carrying an electric contact, a second strip secured at one end to said casing and having a cooperating contact, means for adjusting said cooperating contact carried by said casing, said casing being provided with a Window adjacent one of said ele-- ments.

3. In an arc controlling thermostat, a pair of oppositely disposed thermostatic plates secured together end-to-end to form a strip,

said plates having slits therein, a base member, one end of said strip being attached to said base, a contact carried by the other end of said strip and a relatively fixed contact cooperating with said first mentioned contact.

' 4. In an arc controlling thermostat, a twopart casing, a thermostatic device carried by one of said parts, a movable and a relatively fixed contact carried by said device, an additional contact-associated with each of said first mentioned contacts, contacts carried by I the other of said parts adapted to cooperate with said additional contacts when said casings is in a closed posit on, one of said parts having a light-admitting opening.

In testimony whereof I have aflixed my signature.

MARTIN L. PATTERSON. 

